The present invention relates to probing of electrical circuitry on a substrate, such as a circuit board, and more particularly surface mount probe point socket and system that replaces current square pin probe point contacts.
The electronics industry populates circuit boards and the like with square pins to provide probing points for measurement probes. The measurement probe has either a socket type probe point that fits over the square pin or a needle type probe point that is placed on the square pin. The circuit board is laid out with circuit traces that electrically connect the various electrical elements on the board. Through holes are formed in the board that intersect the traces in the board and accept the square pins. The square pins are soldered to the traces to electrically couple the square pins to the traces and provide circuit continuity. The use of square pin contacts has proven to be an efficient and cost effective way of probing electronic circuitry on a circuit board.
With the increasing speed of electronic components, the use of square pin contacts are proving to be a problem. At higher frequencies, the square pin contacts add capacitance and inductance at the probe tip of the measurement probe which affects the quality of the measured signal. In addition, the square pin contacts act as radiating antennas when high speed edge signals are applied to the contacts.
What is needed is a replacement for the square pin contact that is compatible with the high frequency circuits of electronic equipment. The replacement needs to be physically as small as possible so as not to add inductance and capacitance to the circuit trace or to the measurement probe tip. The replacement further needs to be structurally strong enough to support the measurement probe for hands free probing of the device under test. The replacement also needs to be flexible enough to support various types of probing applications, such as differential probing of the device under test.
Accordingly, the present invention is to a surface mount probe point socket attachable to circuit traces or contact pads of a substrate for receiving a probe point of a high frequency measurement probe. The probe point socket has an electrically conductive housing having a base and socket with the socket extending from the base and having a bore enclosed by an exterior wall. The base has a length and width sufficient for attaching the housing to the circuit trace or contact pad while adding minimal inductance and capacitance to the circuit trace or pad. The socket has a height and diameter for supporting the measurement probe in the housing while adding minimal inductance and capacitance to the measurement probe. A probe point contact is disposed in the bore of the socket for receiving the probe point of the measurement probe to secure the probe in the housing.
In one configuration of the housing, the socket has vertically disposed slots formed in the exterior wall while in a second configuration the socket has a horizontal machined groove formed in the exterior wall of the socket near the base. In a further configuration, the rectangular base is notched on the underside below the socket and grooves formed on the top side of the base adjacent to the socket. The apex of the groove provides a stress concentration line in the socket or base that allows the socket to break away from the base if probe secured in the socket is accidentally hit. The probe point contact has a first configuration having inwardly disposed fingers extending from a frame. In a alternative configuration, the probe point contact is formed an electrically conductive elastomer having sufficient tensile strength, compression set, hardness, deflection force, elongation and percent recovery for repeatably securing the measurement probe in the housing.
Multiple surface mount probe point sockets may be used in a surface mount probe point socket system for receiving probe points of a high frequency differential measurement probe. A non-conductive alignment gage is provides having first and second apertures formed therein. Each aperture receives one of the socket of first and second housing for positioning the housing on the adjacent circuit traces. The bases of the housing are attached to the adjacent circuit traces or contact pads and the probe points of the differential measurement probe are secured in the probe point contacts in the sockets of the housing.
The objects, advantages and novel features of the present invention are apparent from the following detailed description when read in conjunction with appended claims and attached drawings.